Arc lamp



July 28, 1931.' J. H. WAGENHORS'I? Q 5 Fil ed June 4 Sheets-Sheet 1' ly.931. J. H. WAGENHORST 1,816,554 ARC Llulr i iled June 1, 1929 4Sheets-Sheet 2 1 |||nnmnmmrfil t' llllllllllllilllllllllllllllll v J v a13 11 73 ATTORNEYS .1. H. wAssNHoRs'r Anc LAIP Filbd June 1, 1929 4Shasta-Sheet 3 iNVENTOR fines/27V eaZars;

44 ATTORNEYS July 28, 1931. J. H. WAGENHORST 6,

' ARC LAMP Filed June 1, 1929 4 Sheets-Sheet 4 Ill]! INVENTOR Q, 79' WIBY W J47 ATTORNEY 5 Patented July 28, 1931 PATENT QFFICE JAMES H.WAGENHOBST, OF DETROIT, MICHIGAN ARC LAM]? Application filed June 1,1929. Serial No. 367,730.

My invention relates to improvements in arc lamps and has to do, moreparticularly, with the eflicient control of the movable electrodes in alamp employing two or more arcs and, further, with the construction ofthe reflector, within which the arcs are drawn, the housing enclosingthe operating mechanism of the lamp and the means by which these partsare mounted.

Heretofore, in arc lamps having two or more arcs, it has been thepractice to use a clutch for each of the movable electrodes and theresult has been that, after the lamp has burned for sometime, theclutches do not act to feed or separate the carbons uniformly so thatthere is a variation in the length of the arcs and the light intensity.The principal object of my invention is to provide a means forcontrolling the movable arcs, which shall be effective so as to alwayscause a uniform separation of the electrodes so that all the arcs willbe of uniform light intensity. A further object of my invention is toprovide a single clutch controlling all of the movable electrodes andpermitting relative adjustment of the movable electrodes with respect toeach other, when the clutch is in releasing position. A further objectof my invention is to provide a simple, inexpensive but highly eflicientare lamp construction which will I lend itself very readily totherapeutic uses. A further object of my invention is to provide an arclamp in which a central staff forms the backbone of the structure andsupports the reflector and the housing for the lamp operating mechanism,which is carried on the top of the reflector.

Further objects, and objects relating to details and economies ofconstruction and operation will definitely appear from the detaileddescription to follow. In one instance, I accomplish the objects of myinvention by the devices and means set forth in the followingspecification. My invention is clearly deiined and pointed out in theappended claims. A structure constituting a preferred embodiment of myinvention is illustrated in the accompanying electrodes, in a lamphaving two or more drawings, forming a part of this specification, inwhich:

Figure l is a perspective view of an arc lamp en'ibodying my invention,with the swinging front wall of the housing opened,

Fig. 2 is a central, vertical, sectional view through the lamp,

Fig. 3 is a transverse, vertical, sectional view through the lamp, thereflector hoods being moved to open position,

Fig. 4 is a horizontal, sectional View, taken on the line %4l of Fig. 2,

Fig. 5 is a horizontal, sectional view, taken on the line 55 of Fig. 2,

Fig. 6 is a detail, sectional view taken on the line 6 6 of Fig. 2,

Fig. 7 is a fragmentary, sectional view showing the cooperation of theclutch and the control rods, the clutch being shown in releasingposition in dotted lines,

Fig. 8 is a fragmentary plan view of the clutch with the control rodsshown in sec tion, and

Fig. 9 is a perspective view of the clutch member.

In the drawings, the same reference numerals refer to the same partsthroughout the several views.

In general, my invention consists in providing a singlev clutch forcontrolling a plurality of movable electrodes, which clutch, when inreleasing position, permits relative movement of the electrodes. Ipropose to provide control rods with which the single clutch coacts,said control rods being attached to the corresponding mo ableelectrodes. For instance, electrode holders may be fastened to the upperends of the movable electrodes and the control rods may be secured tosaid electrode holders. My invention further consists in providing areflector which is mounted upon the upper end of a central staff and ahousing mounted on top of the reflector and enclosing the operatingmechanism of the lamp, the stationary electrodes being supported withinthe reflector by the staff, while the movable electrodes depend from theoperating mechanism through the top wall 0;. the reflectorinto alinementwith the stationary electrodes. 100

by means of the bolts 25.

The central supporting staff may well be tubular and this permits thecontrol rods, which are centrally arranged, to be slidable in the upperend of the staff, thus making for a more simple and compact structure.

Referring to the numbered parts of the drawings, in which I haveillustrated a preferred embodiment of my invention, the central tubularstaff 11 is mounted upon the upperend of a standard 10. This staff 11extends through the bottom wall of thereflector and the upper endthereof engages and is fastened to the top wall of the reflector. A nut12 screwed on the lower end of the staff 11 engages'the outer face ofthebottom wall of the reflector, so that the parts are held rigidlytogether. This nut 12 may also be screwed upon the upper end of thestandard 10. Laterally-extending flanges 18 are provided on the upperend of the staff 11, by which that staff is attached to the top wall ofthe reflector. The reflector includes bottom, top and end walls, thesides of the reflector being open, except as they may be closed by thehinged reflector hoods.

The bottom wall is dished and comprises the central portion 14 and theupwardly inclined side and end portions 15. The end walls 16 extendupwardly from the upper edges of the end portions of the bottom wall andconnect with the top wall 17. An inner sheet metal plate 18 is fastenedto the top wall and has end portions 19 which extend downwardly parallelto the end walls 16, but are spaced therefrom by means of the bolts 20and the spacing washers 21. This provides a space between the end walls16 and the end portions 19, within which the end members of thereflector hoods may move. A reflector hood is hinged at each side of thereflector and each hood comprises the body portion 22 and the endmembers 23, which end members are adapted to move between the end walls16 and the portions 19 of the reflector. The upper edge of the body 22of each reflector hood is curved, as at 24, and hinged to the top of thereflector These reflector hoods may be opened, as shown in Fig. 3, inorder to divert the light coming from the res through the side openingsof the reflector or one or both of these hoods may be swung to closedposition, thus closing the side openings in the reflector. The edges ofthe top wall 17 of the reflector are folded under the inner plate 18 andsecured thereto, as shown at 26 in Fig. 3. A layer of asbestos board 27is secured to the top wall 17 by the bolts 28, and forms the bottom ofthe housing mounted upon the top of the refleetor. The reflector isfISJQDQCl to the upper end of the central staff 11 by the bolts 29extending through the flanges 13 and through the top wall of thereflector and the asnestos board 27.

-mechanism of the lamp.

clamping members 49. .members 51 are provided which have The housingmounted upon the top of the reflector comprises end walls 30 and a fixedside wall 31. The lower portions of said side and end walls are bentinwardly, at 32, beneath the asbestos board 27, and the bolts 28 passthrough these inturned flanges, thereby securing the housing in positionon the top of the reflector. Both the side and end walls of the housingare provided with a plurality of louvcrs 33, which admit air,permit-ting it to circulate through the housing for the purpose ofcooling the operating Opposite the fixed side wall 31 of the housing,there is a hinged side wall 34, also provided with louvers having aninturned stiffening flange 36. This side wall 34 is hinged at the bottomof the housing "by means of the bolts 35. The upper portion of the fixedside wall 31 is inclined forwardly, at 37, while the upper portions ofthe end walls 30 are inclined toward each other, at 38, as shown in Fig.2. The swinging side wall has a correspondingly inclined upper portion39. A bracket is secured to the fixed side wall 31 by the bolts 41-.This bracket has a portion 42 which extends across the open top of thehousing and carries an eye 43 by means of which the apparatus may besuspended, if it is desired to remove the staff 11 from the standard 10and suspend the lamp. The forward portion 44 of the bracket is bentdownwardly, as shown 1'11 Fig. 3, and has a slot 45 receiving afastening bolt 46. The nut upon this bolt can be backed up and, when theswinging side wall is moved to closed position, the bolt 46 will bereceived in a notch 47 in the upper edge thereof. The nut 46 can then beturned down to fasten the swinging side wall in closed positlon.

A pair of stationary electrodes 48 are supported by the central staff 11within the reflector, these electrodes being located one on each side ofthe central staff. These stationary electrodes are so supported from thecentral staff that they are insulated from each other, and from thecentral staff, by the clamping members, best shown in Fig. The supportfor the stationary electrodes comprises a pair of clamping members 49,having half-round portions at one end adapted to embrace the centralstaff and smaller half-round portions at the opposite end to embrace oneof the stationary electrodes. A strip 50 of insulating material isinterposed between the staff 11 and the Similar clamping halfroundportions at one end adapted to embrace the adj-acent portions of theclamping members 49, and curved portions at the other end to embrace thecorresponding stationary electrode 48. A strip 52 of insulating materialis interposed between. the

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clamping members 51 and the clamping members 49. These clamping membersare all secured together by means of the bolts 53, which clamp themrigidly in position pon the central staff. The stationary electrodes maybe clamped in the outer ends of these clamping members by the bolts 54,which are provided with thumb nuts and also constitute terminals towhich the circuit wires are connected. Blocks 76 of insu lating materialare fastened to the bottom wall of the reflector, thereby preventingshort-circuiting through the reflector in case the electrodes should bedisplaced.

The movable electrodes 55 extend from the housing through the holes 56,formed in the asbestos board 27 and the top wall of the reflector, inalinement with the stationary electrodes 48. Plates 57 are secured tothe top of the'asbestos panel 27 and have openings in line with theholes 56 through which the movable electrodes 55 pass. An electrodeholder is fastened to the upper end of each of the movable electrodes 55and extends laterally therefrom toward the center of the housing. Eachof these electrode holders comprises a pair of clamping mem here 58 (seeFig. 6), having at one end the half-round portions 59 adapted to embracethe movable electrode 55, and, at the other end, the squared portions 60adapted to be clamped about a squared rod 61. The electrode holder,however, is insulated from the squared rod 61 by the strip of insulation62 interposed between the clamping members 58 and said rod 61. Theclamping members 58 are clamped about the rod 61 by the bolts 63, andmay be clamped about the electrode by the bolt 64, which serves also aterminal for the circuit wire connected thereto.

A control rod 65 is provided for each of the movable electrodes. Thesecontrol rods are arranged side by side, as shown in Fig. 2, and withtheir lower ends slidably mounted'in the upper portion of the centraltubular staff 11, said rods extending downwardly through a hole 66formed in the top wall of the reflector. The legs of a staple 67 areinserted through the staff 11 on opposite sides of the rods 65, so as toprevent tilting and displacement of the rods in clamped in the electrodeholder as already described. By this means the control rod C3 65 isrigidly attached to the corresponding movable electrode 55 so that itextends parallel thereto.

I provide a single clutch oo-acting with the control rods 65 to controlboth of the movable electrodes 55. This clutch member 68 has anelongated opening 69 through which the control rods 65 pass, there beingsmaller offset notches 70 at each end of the large elongated opening 69,as shown in Fig. 8. When this clutch is in the dotted line position,shown in Fig. 7, the control rods 65 are free to move longitudinallythrough the clutch member and relative to each other. lVhen, however,the clutch is tilted, as shown in full lines in Fig. 7, it

-will grip the two control rods, hold them against movement relative toeach other, and permit them to be lifted by the clutch member. Theclutch operating link 71 has its lower end turned laterally, at 72, andinserted in a bore 73 formed in the end of the clutch member. Theremoval of the end of the link from this bore is prevented by the pin7%, inserted transversely through the clutch and engaging the groove 75in the end portion 72 of the link. The upper end of this link isconnected to the clutch operating mechanism.

The operating solenoid 79 is supported from one end wall of the housingby means of the spring supports 7 8, which are carried by the blocks 77fastened to that end wall. r1? 3 ine solenoid core 50 is connected by aspring 81 to one arm of the U-shaped operatin lever 82. This lever ispivoted on the pin 83 carried by the bracket l-O. An eye 8% formed inthe upper end of the link 71 is hooked through a hole 85 in the onpositeend of this operating lever. A dash pot 86 is suspended from the samearm of the lever and a plunger 88 works in this dash pot. This plungeris carried on the upper end of a plunger rod 87 which is fastened to thetop of the reflector 2nd e tends upwardly therefrom. A slab ofinsulating material, such as asbestos board, is fastened to the top ofthe reflector and extends upwardly within the housing but spaced fromone end wall thereof so as to form a chamber with said end wall. Thisslab of insulating material is secured in place by the bracket 90 whichis fastened to the top of the reflector, and held in spaced relationfrom the end wall by the bolt 9i and the spacing sleeve 92 at the upperend thereof. In the chamber thus formed between the end wall and theslab, the resistance coils 93 are mounted upon the slab 89. It will beseen that the upper end of this chamber is open and air will enterthrough the louvers in the end wall and the adjacent portions of theside walls, and this current of air will pass upwardly over theresistance coils and out through the open top of the housing. Thisarrangement aids materially in keeping these coils from overheating.

The operating current is brought through the main Wires 94 to the maincontrol switch 95 mounted on the bottom of the reflector. From thisswitch, one wire 96 leads to the terminal for the left-hand lowerelectrode 48 in Fig. 2. From this electrode the current passes to thecorresponding movable electrode 55. From the electrode holder attachedto the upper end of this movable electrode, the current passes throughthe wire 97 to the upper end of the solenoid 79, and from the lower endof said solenoid through the wire 98 to the terminal 99 at one end ofthe resistance coil From the terminal 100, at the other end of saidrcuistance coil, the current passes through wire 101 to the electrodehoi fastened to the upper end of the right-hand movable electrode shownin Fig. 2, and, thence, through this electrode and the correspondingstationary electrode 48 and the wire 102 back to the switch. It will beseen that the two pairs of electrodes, the solenoid and the resistancecoils are all connected in series.

From the description of the parts given above the operation of t iis arelamp should be very readily understood. In Fig. 2, the electrodes areshown in the position they occupy when both arcs have been drawn and arein operation. If either are should be extinguished, or the circuitshould be interrupted for any reason, the solenoid '79 .beingde-energized will permit the core 80 to rise, thus permitting theopposite end of the operating lever 82 to drop and the clutch 68 to dropto its releasing position. As soon as this happens, the control rods 65will be released and the weight of these rods and the electrodesconnected thereto will cause these parts to move downwardly until themovable electrodes contact with the upper ends of the stationaryelectrodes l8, whereupon the circuit will be re-established, thesolenoid energized once more, the clutch lifted to grip the control rodsand draw both arcs simultaneously, effecting an equal separation of theelectrodes since both the upper electrodes are moved together. If, forany reason, one electrode should burn away more rapidly than the other,there will. be a relative movement of the control rods and the connectedelectrodes with respect to each other when the clutch is in releasingposition, thus compensating for the difference in the rate at which theelectrodes are consumed, so that, when the arcs are next formed, theelectrodes will again be separated an equal amount. This means that thearcs are always of the same light intensity and this results in a muchmore eflicient and effective working of the lamp. Furthermore, as theelectrodes burn away and the arcs are thus gradually lengthened,

the resistance in the circuit gradually increases, thus decreasing thepull of the solenoid 7 9 upon core 80 and gradually lowering link 71until clutch 68 engages plate 27. When this happens the clutch tiltssufiiciently to release the control rods and they are loweredsimultaneously a slight distance, decreasing the length of the arcs andthe resistance so that the pull of the solenoid on its core is slightlyincreased to lift the clutch from engagement with plate 27 causing it totilt and clutch the control rods once more. Thus the electrodes will befed by small successive increments, simuL taneously, maintaining thearcs substantially constant Without breakng the circuit. The controlrods having been forced tightly against each other by the clutch, willdescend simultaneously as one unit when the clutch touches plate 27 andreleases, but if the rods drop until upper and lower electrodes contact,relative movement of the control rods may then take place until bothpairs of electrodes contact.

It will be observed that the central stall 11 constitutes the backboneof the lamp, the reflector being mounted upon this and the operatingmechanism being carried by the housing which is mounted on top of thereflector. Furthermore, the reflector hoods are hinged to the reflectorand adapted to close the side openings thereof and may be opened so thatthe light from the arcs may be directed at one side or both as required.

I am aware that the particular construction illustrated in thisapplication may be changed considerably, without departing from thespirit of my invention, and, therefore, I claim my invention broadly, asindicated by the appended claims.

hat I claim is:

1. In an arc lamp, the combination of a pair of stationary electrodes, apair of movabieelectrodes having rod'like portions constitutingextensions thereof, a single clutch coacting with said rod-likeextensions and means for actuating said clutch.

2. In an arc lamp, the combination of a plurality of stationaryelectrodes, a plurality of electrodes independently movable with respectto each other and cooperating with said stationary electrodes to providea plurality of arcs, a single clutch restraining said movable electrodesas .a unit, means providing partial release of said clutch and offectingequal feeding of said movable electrodes when the current passingthrough the arcs is decreased due to electrode consumption and providingcomplete release of said clutch and permitting differential movement ofsaid electrodes when the current is interrupted.

3. In an arc lamp, the combination of a pair of stationary electrodes, apair of movable electrodes cooperating therewith, a control rod attachedto each of said movable electrodes, a single clutch co-acting with saidcontrol rods, and means for actuating said clutch.

4. In an arc lamp, the combination of a pair of stationary electrodes, apair of movable electrodes cooperating therewith, a control rod fastenedto each movable electrode, said control rods being longitudinallymovable relative to each other, a single clutch co-acting with said.control rods, and means for actuating said clutch.

5. In an arc lamp, the combination of a pair of spaced stationaryelectrodes, a pair of movable electrodes cooperating therewith, acontrol rod fastened to each movable electrode, said control rods beingarranged side by side and longitudinally movable with respect to eachother, a single clutch co-acting with both of said control rods, andmeans for actuating said clutch.

G. In an arc lamp, the combination of a pair of stationary electrodes, apair of movable electrodes cooperating therewith, electrode holdersfastened to the upper ends of said movable electrodes, a pair ofrelatively shiftable control rods secured to said electrode holders, asingle clutch co-acting with said control rods, and means for actuatingsaid clutch.

7. In an arc lamp,-the combination of a pair of spaced stationaryelectrodes, a pair of movable electrodes cooperating therewith, anelectrode holder secured to the upper end of each movable electrode andextending laterally therefrom, control rods centrally arranged andcarried by said electrode holders, a single clutch (co-acting with saidcontrol rods, and means for actuating said clutch.

8. In an arc lamp, the combination of a pair of stationary electrodes, apair of movable electrodes cooperating therewith to draw a pair of arcssimultaneously, a single clutch controlling said movable electrodes andpermitting independent movement thereof when in releasing position, andmeans for actuating said clutch.

9. In an arc lamp, the combination of a pair of stationary electrodes, aair of movable electrodes cooperating th-cre 'ith, electrode holdersclamped about the upper ends of said movable electrodes and extendinglaterally therefrom, a pair of tubes arranged side by side, U-shapedrods each having one leg fixed in the upper end of one of said tubes andthe other leg secured to one of said electrode holders, a single clutchcoacting with said tubes, and means for actuating said clutch.

10. In an arc lamp, the combination of a pair of stationary electrodes,a pair of movable electrodes cooperating tnerewith to draw a pair ofarcs simultaneously, a single clutch controlling both movable electrodesand permitting relative movement thereof when in releasing position, aclutch-operating solenoid, an armature therefor, and operatingconnections between said clutch and armature.

11. In an arc lamp, the combination of a pair of stationary electrodes,a pair of movable electrodes cooperating therewith, a control rodfastened to each of said movable electrodes, a single clutch co-actingwith both of said rods, a clutch-operating solenoid, an armaturetherefor, and operating connections between said armature and clutch.

12. In an arc lamp, the combination of a central staff, a reflectormounted on the upper end of said staff, a housing mounted on top of saidreflector, a stationary electrode supported by said staff Within thereflector, electrode-operating mechanism enclosed within said housing,and a movable electrode depending therefrom into the reflector andcooperating with the stationary electrode.

13. In an arc lamp, the combination of a central staff, a reflectormounted on the upper end of said staff, a housing mounted on top of saidreflector, a pair of stationary electrodes supported by said staff onopposite sides thereof within the reflector, electrode operatingmechanism enclosed within said housing, and a pair of movable electrodesdepending therefrom into the reflector in alignment with the stationaryelectrodes.

14. In an arc lamp, tne combination of a central staff, a reflectormounted on the upper end thereof, a housing mounted on top of saidreflector, a pair of stationary electrodes supported by said staffwithin said reflector, electrode-operating mechanism carried by saidhousing, and a pair of movable electrodes depending therefrom, throughholes in the top wall of said reflector, into cooperative relation withsaid stationary electrodes.

15. In an arc lamp, the combination of a central staff, a reflectormounted on the upper end thereof, a housing mounted on top of saidreflector, a stationary electrode supported by said staff within thereflector, a solenoid supported by the housing, a movable electrodeextending through the top wall. of said reflector into alinement withthe stationary electrode, a clutch controlling the movable electrode, acore for said solenoid,

and operating connections between said clutch and core.

16. In an arc lamp, the combination of a central staff, a reflectormounted on the upper end thereof, a housing mounted on top of saidreflector, a stationary electrode supported by said staff within thereflector, a solenoid carried by said housing, a movable electrodeextending through a hole in the top of said reflector into cooperativerelation with said stationary electrode, a clutch controlling themovable electrode, a lever .pivoted on said housing, a core for saidSole noid connected to one arm of said lever, and a link connecting theopposite arm of said lever and the clutch.

17. In an arc lamp, the combination of a central staff, a reflectormounted on the upper end thereof, a housing mounted on top of saidreflector, a stationary electrode sup ported by said staff within saidreflector, a movable electrode extending through the top of saidreflector into cooperative relation with said stationary electrode, aclutch controlling said movable electrode, a solenoid carried by saidhousing, a lever pivoted on said housing, a core for said solenoidconnected to one arm of said lever, connections between said lever andclutch, a dash-pot suspended from said lever, a plunger rod mounted onthe top of said reflector, and a plunger on the upper end of said rodworking in said dash-pot.

18. In an arc lamp, the combination of a central staff, a reflectormounted on the upper end thereof, a housing mounted on top of saidreflector, cooperating electrodes, electrode-operating mechanismenclosed within said housing, a panel mounted on the top of thereflector and extending upwardly within the housing in spaced relationto an end wall thereof, and a resistance coil connected in series withsaid electrodes and mounted on said panel in the chamber formed thereby,

said coil being separated from the operating mechanism by sa d panel.

19, In an arc lamp, the comblnation of a central tubular shaft, areflector mounted on the upper end thereof, a pair of stationaryelectrodes supported by said staff within said reflector, a pair ofmovable electrodes extending through the top wall of the, re-

flector into cooperative relation with the stationary electrodes,control rods fastened to the movable electrodes and extending into thetubular staff, a single clutch co-acting with said control rods, andmeans for actuating said clutch.

20. In an ar lamp, the combination of a central tubular staff, areflector mounted on the upper end thereof, a pair of stationaryelectrodes supported by said staff on op p'osite sides thereof withinthe reflector, a pair of movable electrodes extending through the top ofsaid reflector in alinement with the stationary electrodes, elecf trodeholders fixed to the movable electrodes and extending laterallytherefrom, a pair of control rods secured to the electrode holders andslid-ably mounted in the upper end of said staff, a single clutchpositioned above the top wall of the reflector and engagingboth controlrods, and means for actuating said clutch.

21;. In an arc lamp, the combination of a central tubular staff, areflector mounted on the upper end thereof, a housing mounted on top ofthe reflector, a pair of stationary electrodes supported by the staffwithin the reflector, a pair of movable electrodes extending through thetop of said reflector in alinement with the stationary electrodes,electrodes holders fastened to the movable electrodes and extendinglaterally from the upper ends thereof, a pair of control rods secured tosaid holders and depending therefrom into the upper end of said staff, asingle clutch engaging said rods, a clutchoperating solenoid mounted onsaid housing, a core therefor, and connections between the clutch andcore.

22. In an arc lamp, the combination of a reflector having side openings,reflector hoods hinged to the top of the reflector and adapted to closesaid side oicnings, and a housing mounted on top of said reflector.

23. In an arc lamp, the combination of a reflector having a dishedbottom and side openings, reflector hoods hinged to the top of saidreflector and adapted to close the side openings, and a housing mountedon top of the reflector.

24. In an arc lamp, the combination of a reflector having side openings,reflector hoods hinged to the top of the reflector and adapted to closesaid openings, and a housing mounted on the top of the reflector andhaving a swinging side wall.

25. In an arc lamp, the combination of a reflector having rigid top andbottom walls, and a support for the reflector comprising a central staffextending snugly through the bottom wall and secured to and supportingthe reflector from its top wall.

26. In an arc lamp, the combination of a reflector having rigid top andbottom walls, and a combined brace and support for the reflectorcomprising a central tubular staff extending through the bottom wall.secured to and supporting the top wall, and a sleeve mounted about thetubular staff and snugly engaging the outer face of the bottom "wall.

27. In an arc lamp, the combination of a pair of spa en stationaryelectrodes, a pair of movable electrodes cooperating there with, acontrol rod fastened to each movable electrode, said control rods beingarranged side by side, a single clutch bringing the rods tightlytogether for movement as a unit when engaged thereby, and allowingrelative longitudinal movement of the rods when released, and means foractuating the clutch.

AMES H. IVAGENHORST.

